Other primary threats are hybridization, or interbreeding, with non-native salamanders, and predation by non-native species. The threat of hybridization is particularly severe in the Central Coast Range and the Bay Area, and to a lesser extent the Central Valley.

which indicates hybridization is a problem but doesn’t speak to it’s role in species formation.

After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger salamander (A. californiense). Hybridization and backcrossing have been occurring in central California for 50–60 years, or an estimated 15–30 generations. (from the article abstract)

For many years, the tiger salamanders were considered a single polytypic species, A. tigrinum, that had the most widespread geographic distribution of any salamander species in North America. Molecular genetic studies (Shaffer, 1984; Routman, 1993; Templeton et al., 1995; Shaffer and McKnight, 1996) indicate that the tiger salamanders cannot be considered a single species and that the formally recognized subspecies may not be valid taxonomic units. Furthermore, A. tigrinum as currently recognized is paraphyletic with respect to numerous Mexican species, many of which are perennibranchiate forms having restricted geographic distributions. Evolution of perennibranchiate forms probably has occurred numerous times from within the A. tigrinum complex.

Unfortunately, this hybridization has been used by the unscrupulous to avoid listing the California Tiger Salamander on the endangered species list. See here and here. This latter link is interesting in the way it distorts scientific research. If you regularly read Chris Mooney it will sound all too familiar.

Salamanders first appeared in the Jurassic. It is believed that they evolved from lpospondyles such as the microsauria. Salamanders are considered to be the least specialized of amphibians – mainly due to their conservative body plan. One interesting feature in salamander evolution is the secondary loss of bone and it’s replacement with cartilage.

Cladogram

Salamander 2 fossil

Recently, a large number of salamander fossils have been found in volcanic ash in China. The preservation was excellent -including many details of soft tissue anatomy.

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"You may not be willing to admit that you resemble an ape; if your thousandth ancestor is more like an ape than you are, you may, if you wish, call it a coincidence. But if that thousandth ancestor's forebears become progressively more simian as you trace back the geneological lines, you will have to admit that somewhere in your family tree there squats an ape." Earnest Hooten

Charles Darwin

"But I had gradually come, by this time, to see that the Old Testament from its manifestly false history of the world, with the Tower of Babel, the rainbow at sign, etc., etc., and from its attributing to God the feelings of a revengeful tyrant, was no more to be trusted than the sacred books of the Hindoos, or the beliefs of any barbarian." Charles Darwin: The Autobiography